Retina Ready WordPress Logo

<?php
// this is a hack
// assumption is the uploaded image will be 2x size of actual image used
// for example image will be displayed as 225 * 90 px so upload image needs to be 500 * 180
// so image size added using image size would be add_image_size( 'site-logo', '225', '90', true );

$custom_logo_id = get_theme_mod( 'custom_logo' );
$logo = wp_get_attachment_image( $custom_logo_id , 'site-logo');
if ( has_custom_logo() ) {
  //the_custom_logo();
    echo '<a href="'.home_url().'">';
    echo $logo;
    echo '</a>';
}